Mangrove conversion and aquaculture development in Vietnam: A remote sensing-based approach for evaluating the Ramsar Convention on Wetlands   总被引：4，自引：0，他引：4  

Karen C. Seto  Michail Fragkias   《Global Environmental Change》2007,17(3-4):486-500

Remote sensing data have been proposed as a potential tool for monitoring environmental treaties. However, to date, satellite images have been used primarily for visualization, but not for systematic monitoring of treaty compliance. In this paper, we present a methodology to operationalize the use of satellite imagery to assess the impact of the Ramsar Convention on Wetlands. The approach uses time series analysis of landscape pattern metrics to assess land cover conditions before and after designation of Ramsar status to monitor compliance with the Convention. We apply the methodology to two case studies in Vietnam and evaluate the success of Ramsar using four metrics: (1) total mangrove extent; (2) mangrove fragmentation; (3) mangrove density; and (4) aquaculture extent. Results indicate that the Ramsar Convention did not slow the development of aquaculture in the region, but total mangrove extent has remained relatively constant, primarily due to replanting efforts. Yet despite these restoration efforts, the mangroves have become fragmented and survival rates for replanting efforts are low. The methodology is cost effective and especially useful to evaluate Ramsar sites that rely mainly on self-reporting methods and where third parties are not actively involved in the monitoring process. Finally, the case study presented in this paper demonstrates that with the appropriate satellite record, in situ measurements and field observations, remote sensing is a promising technology that can help monitor compliance with international environmental agreements.  相似文献   

Dynamics of floodplain-island groundwater flow in the Okavango Delta, Botswana     

P. Wolski  H.H.G. Savenije   《Journal of Hydrology》2006,320(3-4):283-301

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Biodiversity of the wetlands of the Kakadu Region, northern Australia     

C. Max Finlayson  John Lowry  Maria Grazia Bellio  Suthidha Nou  Robert Pidgeon  Dave Walden  Chris Humphrey  Gary Fox 《Aquatic Sciences - Research Across Boundaries》2006,68(3):374-399

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Fine Resolution Palaeoecology Confirms Anthropogenic Impact During the Late Holocene in the Lower Hawkesbury Valley,NSW     

Adrian G. Johnson 《The Australian geographer》2000,31(2):209-235

This study reconstructs environmental conditions at Mill Creek, within the lower Hawkesbury-Nepean Valley, by the use of fine resolution palaeoecological studies of sediments. Archaeological surveys and historical accounts are used to investigate ecosystem response to known human activities. Research found that during prehistoric times (between 820 BP and the 1790s), the study area was well vegetated with dry sclerophyll communities on the valley sides, and a highly productive wetland community occupied the moist valley floor. Valley sides were generally stable, and little fire was evident in the landscape. Sediment was mainly deposited on the valley floor from the Hawkesbury-Nepean River during flood. After European settlement in the 1790s, sedimentation rates and charcoal preserved within sediments increased significantly, probably due to agricultural and clearing practices, both locally and upstream. Consequently, vegetation communities were altered. In 1967, the study area became part of Dharug National Park. Forestry and agricultural activities were excluded from the catchment, and the fire regime was reduced in frequency. Present-day vegetation communities appear to be becoming more like those that prevailed during prehistoric times. However, sedimentation rates remain elevated due to continued disturbance to the greater Hawkesbury River catchment. Recent poor water quality, coupled with a succession of floods on the Hawkesbury River, has increased wetland productivity levels, and their spatial extent, at Mill Creek.  相似文献   

Significance of enhanced infiltration due to groundwater extraction on the disappearance of a headwater lagoon system: Toluca Basin, Mexico   总被引：1，自引：0，他引：1  

D. L. Rudolph  R. Sultan  J. Garfias  R. G. McLaren 《Hydrogeology Journal》2006,14(1-2):115-130

Mexico City relies significantly on groundwater resources drawn from the Sistema Lerma well field located in the Toluca Basin, Mexico. Enhanced infiltration caused by groundwater extraction is suspected to be both a prime factor in the disappearance of a lagoon system at the Toluca Basin and a potential risk to long-term groundwater quality. A combined approach of field investigation and numerical modeling was adopted to assess the groundwater-surface water interactions within the lagoon system. Potentiometric data indicate that current downward vertical hydraulic gradients below the lagoon and surrounding wetland area are extremely low suggesting very slow infiltration rates. Geochemical and isotope data from surface water and groundwater sampling also indicate that very little surface water infiltration has occurred. Numerical simulations demonstrate that enhanced surface water infiltration is unlikely to be the primary cause in the significant reduction in size of the lagoon system. Other factors such as modifications to the surface water drainage system and capture of spring flow from the surrounding mountainous regions are likely more significant. Simulations also suggest that contaminants originating in the lagoon system are currently entering nearby production wells although the total contaminant mass flux to the wells is still very low and significantly diluted.

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Resumen La Ciudad de México depende significativamente de los recursos de aguas subterráneas obtenidos del campo de pozos Sistema Lerma ubicado en la Cuenca Toluca, oeste de la Cuenca de México. Se sospecha que la infiltración estimulada causada por extracción intensiva de aguas subterráneas es un factor principal en la desaparición de un sistema de lagunas en la cabeceras del Río Lerma en el centro de México y un riesgo potencial para la calidad de aguas subterráneas a largo plazo en la región. Se adoptó un enfoque combinado de investigación de campo y modelizado numérico para evaluar las interacciones de agua superficial-agua subterránea dentro del sistema de lagunas. Datos potenciométricos indican que los gradientes hidráulicos verticales descendentes actuales, ubicados por debajo de la laguna y vecina área de humedales, son extremadamente bajos sugiriendo ritmos de infiltración muy lentos. Datos geoquímicos e isotópicos provenientes del muestreo de agua superficial y subterránea también indican que ha ocurrido muy poca infiltración de agua superficial. Las simulaciones numéricas demuestran cuantitativamente que no es probable que la infiltración estimulada de agua superficial sea la causa principal en la reducción significativa del tamaño del sistema de lagunas en la cabecera. Otros factores tal como modificaciones al sistema superficial de drenaje de agua y captura de flujo de manantial en las regiones montañosas vecinas son probablemente más significativos. Las simulaciones también sugieren que los contaminantes que se originan en el sistema de lagunas están actualmente ingresando a pozos de producción cercanos aunque el flujo de masa contaminante total a los pozos es aún muy bajo y diluido significativamente en los volúmenes grandes de extracción. La magnitud de la amenaza a largo plazo a la calidad del agua subterránea en los pozos de producción Sistema Lerma proveniente de contaminantes infiltrados es una preocupación y amerita estudios futuros.

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Résumé La Cité de Mexico dépend significativement des ressources en eau souterraine pompées au site de captages de Sistema Lerma, dans le Bassin de Toluca, à lOuest du Bassin de Mexico. Laugmentation de linfiltration, causée par lextraction extensive des eaux souterraines, est suspectée dêtre à la fois un facteur primaire de la disparition dun système de lagons en amont de la rivière Lerma au centre de Mexico, et un risque potentiel à long-terme pour la qualité de leau souterraine dans la région. Uen approche combinée détudes de terrain et de modélisation numérique a été adoptée pour estimer les interactions entre les eaux de surface et les eaux souterraines, au sein du système de lagons. Les données potentiométriques indiquent que les gradients hydrauliques verticaux descendants sont très bas au niveau des lagons, ce qui suppose un taux dinfiltration faible. Les données géochimiques et isotopiques provenant des eaux de surface et souterraines, indiquent également que peu deau de surface sinfiltrent. La simulation numérique démontre quantitativement que laugmentation de linfiltration des eaux de surface nest probablement pas la première cause de réduction des lagons. Dautres facteurs, tels que les modifications du drainage des eaux de surface, laménagement en captage des sources situées aux pieds des montagnes environnantes, sont probablement plus importants. Les simulations suggèrent également que les contaminants provenant des lagons se retrouvent également dans les captages les plus proches, bien que le flux total de contaminants entrant dans les captages reste faible. Les volumes dextraction étant très important ils diluent effectivement les contaminants. Les effets à long-terme de lextraction critique au niveau des forages de Sistema Lerma et de la dégradation de la qualité des eaux souterraines par les contaminants, nécessite une grande attention pour le futur.

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黄淮海地区湿地水生态过程、水环境效应及生态安全调控   总被引：12，自引：1，他引：11  

杨志峰  崔保山  黄国和  白军红  孙涛  李晓文  刘新会 《地球科学进展》2006,21(11):1119-1126

围绕国家重点基础研究发展计划(973计划)项目“黄淮海地区湿地水生态过程、水环境效应及生态安全调控”,介绍了湿地水生态过程、水环境效应和生态安全调控研究对我国社会与科技发展的意义、研究现状和发展趋势、拟解决的关键科学问题、主要研究内容和研究总体方案。该项研究的最终目标是发展一套集河流、湖沼、河口等湿地系统组分于一体的湿地系统层面上的湿地学理论,解决我国湿地研究面临的一系列基础科学问题,有效协调区域社会经济发展与湿地保护之间的矛盾,为建立不同目标下湿地系统整体调控模式,构建生态、社会和经济相互协调及环境友好型社会体系提供理论和技术支撑。  相似文献   

Hydrology and plant survival in excavated depressions near an earthen dam in north-central Texas     

Lynde L. Williams  Paul F. Hudak 《Environmental Geology》2005,48(6):795-804

This investigation examined plant survival and water sources for small depressions excavated to build an earthen dam and nature trail in north-central Texas, USA. These “inadvertent wetlands” occupy part of an outdoor education facility, overlying alluvial deposits of the Trinity River. A large lake behind the earthen dam strongly influences surface water and groundwater levels in the area. Excavated depressions receive direct precipitation, runoff, and groundwater inputs, losing water by seepage and evapotranspiration. Hydroperiods varied with location and water input: excavations receiving groundwater held water year round; others periodically desiccated. Groundwater-fed depressions had higher salinity; however, the highest average value (1,304 μS/cm) was within the freshwater range. A total of 66 to 75% of emergent and floating wetland species planted in three depressions survived after 2 years. The developing wetlands appear viable under hydrologic conditions typical of the study period. Ultimately, variable hydroperiods among wetlands, and water level fluctuations within individual wetlands, may foster diverse plant-species compositions. Depressed lake levels following long-term drought or increased water demands pose the greatest threat to the developing wetlands.  相似文献   

从第七届国际湿地会议看全球湿地研究热点及进展   总被引：16，自引：6，他引：16  

左平  宋长春  钦佩 《湿地科学》2005,3(1):66-73

通过介绍在荷兰乌得勒支市召开的第七届国际湿地会议的主要报告内容和信息 ,结合国外有关湿地研究的热点和进展 ,以及我国近年来有关的湿地研究工作 ,分析了湿地科学这一学科的基本理论和未来的发展动向和趋势 ,即立足于湿地的基本特征 ,及综合水文学、土壤学、生物地球化学、生态学、地理学等多学科的基础理论和应用技术 ,为湿地生态系统的可持续发展和合理利用提供正确的方向和决策。  相似文献   

广州山水格局及其保护   总被引：2，自引：2，他引：2  

梁国昭 《热带地理》2001,21(1):1-6

广州“山水”的概念，不应仅仅理解为“云山珠水”。从越秀山、白云山起，向东北绵延200km的山脉，以及相辅的山丘台地，构成广州山的格局；广州的水，除了珠江以外，还应包括众多的河涌、湖泊、沼泽、滩涂等湿地。这些山地和湿地，对于广州的生态环境有十分重要的作用。保护和合理利用广州优越的山水条件，是建设现代化山水城市的必然要求。  相似文献   

大庆龙凤湿地须浮鸥巢址选择研究     

陈雪龙  杨焕民  齐艳萍  王晓龙 《湿地科学》2012,10(3):339-343

为了认知影响须浮鸥(Chlidonias hybridus)营巢的主要环境因素,于2011年6～7月,采用直接观察法和样方法在大庆龙凤湿地自然保护区内对须浮鸥的巢区进行了调查研究.在本次调查中共发现须浮鸥巢73个,逐巢进行了常规测量,并对须浮鸥巢址及附近无巢对照区域的生境进行了调查.主成分分析和独立样本t检验的结果表明,须浮鸥属于集群营巢,而影响须浮鸥巢址选择的主要因素依次为巢下水深、巢距植物距离、巢周明水面积、植物高度、植物密度和巢距干扰源距离.其中,前3个因素影响须浮鸥生境中食物的供给条件,后3个因素影响须浮鸥巢的隐蔽条件.须浮鸥选择巢址的条件是能提供丰富食物且具有较好隐蔽条件的生境.  相似文献